“Heat assisted magnetic recording,” optical assisted recording or thermal assisted recording (collectively hereinafter HAMR), generally refers to the concept of locally heating a recording medium to reduce the coercivity of the recording medium so that an applied magnetic writing field can more easily affect magnetization of the recording medium during a temporary magnetic softening of the recording medium caused by the local heating. HAMR allows for the use of small grain media, which is desirable for recording at increased areal densities, with a larger magnetic anisotropy at room temperature assuring a sufficient thermal stability. HAMR can be applied to any type of storage media, including for example, tilted media, longitudinal media, perpendicular media, and/or patterned media.
To locally heat up the media in HAMR, optical transducers, such as near field transducers (NFTs) are often incorporated into the head in order to focus laser light to a nanometer sized area. An NFT is able to confine light far beyond the diffraction limit by generating localized surface Plasmon (LSP).
The feature size of NFTs in a HAMR head is normally very small in order to get the right resonance frequency, thermal spot size and high coupling efficiency. For a “lollipop” shaped NFT, the disk size is often only about 200 nm in diameter. NFTs are often embedded in waveguide materials, which couple the laser light onto the NFT from outside. Waveguide materials normally have very poor thermal conductance. All of these factors result in enormous temperature increases at the region of the NFT, much higher than what thermal recording requires. This can lead to overheating and exceedingly elevated temperatures which can lead to reliability issues for HAMR heads. Therefore, there remains a need for NFTs that are less susceptible to overheating.